Hi, I’m Kai Castledine.
Exploring security, systems, business, and everything in between.
The Story so far
About Me
I work at the intersection of security, entrepreneurship, and hands-on advisory.
KSEC was founded on a simple idea: Real security starts with understanding, not just of systems, but of the people who use them. That philosophy has shaped everything I’ve done since, from building businesses and security service platforms to developing tools that empower individuals and organisations alike.
I believe security is more than a technical challenge, it’s a human one. And often, the biggest breakthroughs come from the spaces between disciplines.
The Things I’ve Built
A selection of companies, ventures, and community projects I’ve created, led, or supported.
KSEC Worldwide
Hands-on hardware hacking tools, embedded devices, and security-focused platforms, built for professionals and educators.
KSEC
Global security training and hardware solutions, delivering innovative tools and knowledge across 80+ countries.
OnlySecurity
Backing the worldwide security community through sponsorship, mentorship, and collaboration at global events.
KSEC Pro Pick
A curated range of lock picking and covert entry tools, trusted by professionals worldwide.
The KSEC Group
A parent entity consolidating KSEC’s operations, training brands, and product lines under one strategic framework.
Castledine Holdings
A private holdings entity for managing group equity, brand IP, and long-term asset strategy.
Castledine & Co
A boutique brand focused on property, capital management, and strategic ventures, the foundation for long-term growth.
BSides Brighton
Backing the UK security community through sponsorship, mentorship, and collaboration at grassroots events.
92%
Client retention
400+
Projects delivered
12+
Hands-on experience
39K
Customers & Contacts
Current Work
Founder of KSEC — Building solutions at the intersection of security, hardware, and education.
Cyber, Risk & Security Advisory — Supporting global clients across cloud infrastructure, containerised environments, and evolving digital systems.
Creator of OnlySecurity — Delivering practical security knowledge for individuals and teams.
Advisor and Collaborator — Helping businesses and organisations rethink how they approach security in a fast-changing world.
Offensive Security Lead
Led and executed complex offensive security programmes, from red teaming and adversary emulation to high-stakes engagements across physical, cloud, and hybrid environments.
Sector Experience
Worked across high-assurance industries including defence, healthcare, aerospace, and financial services (including FTSE 100), aligning security practices to strict regulatory and operational requirements.
Collaborative by Design
Partnered with technical teams, leadership, and stakeholders to embed security into products, pipelines, and processes. Prioritising context and business needs.
Technical In-Depth
Skilled in real-world offensive and defensive techniques, with a foundation in infrastructure, embedded systems, wireless protocols, and cloud-native platforms.
Previous Roles & Education
My path into security has been fast-moving and hands-on. Evolving from infrastructure and support into offensive operations and strategic leadership. These experiences laid the foundation for KSEC and my ventures, blending technical depth with operational insight and entrepreneurial drive.
University at 16
Began a Bachelor’s degree in Computing Science after being fast-tracked from college following a referral by my lecturers.
IT Systems Admin & Support
Worked across multiple companies, gaining experience in SMB/SME infrastructure, troubleshooting, and operations. Laying the groundwork for defence-in-depth.
Security Consultant
Context Information Security (now Accenture Security) – Delivered security testing and advisory for major clients, including those in gov, aviation, and finance.
Head of Offensive Security
Informer (Since acquired by BugCrowd). Led a growing offensive security practice, building out testing capabilities, managing key client relationships, and overseeing technical delivery across engagements.